Draw press



Feb. 12, 1957 Filed June 11, 1952 R. F. DEHN EFAL DRAW PRESS 4Sheets-Sheet 1 INVENTORS Roy F D-EHN lmM- WAR 4 Sheets-Sheet 2 DRAWPRESS R. F. DEHN El'AL Feb. 12, 1957 Filed June 11, 1952 INVENTORS Roy1-? DEHN BY WIl/(Ah Win Q, Arron-w Feb. 12, 1957 R. F. DEHN ETAL2,781,015

DRAW PRESS Filed June 11, 1952 4 Sheets-Sheet a INVENTORS Roy E DEHN BYWll/IAM. WARD Feb.

Filed June 11, 1952 R. F. DEHN ET AL DRAW PRESS so 90 no no ran 15a I40I50 so no Ian I50 200 2|o2l5 Q0 A DEHN BY Will/AM E. WARD UnitedStatesPatent (3 DRAW PRESS Roy F. Dehn, Wickliife, and William E. Ward, ShakerHeights, Ohio, assignors to The Cleveiand (Irene & Engineering Company,Wickliife, Ohio, a corporation of Ohio Application June 11, 1952, SerialNo. 292,828

6 Claims. (Ci. 11338) The present invention relates to crank operatedpresses and the like, particularly adapted for deep drawing operations.

The principal object of the present invention is the provision of a newand improved crank operated draw press or the like, having a crankdriven at a substantially constant rate and a ram reciprocated therebythrough mechanism operative to produce a substantially constant,relatively slow rate of movement of the ram throughout the drawingportion of its stroke, and a relatively rapid return movement followingthe drawing stroke.

A more specific object of the invention is the provision of a new andimproved crank operated draw press having a ram connected with the crankpin or eccentric thereof through twopivotally connected leversconstituting a toggle linkage, one of which levers is pivotallyconnected with the crank pin and the other pivotally connected with theram, and means operated in synchronism with movement of the crank toshift the pivotal connection between the two levers to one side of aline through the axis of the crank shaft and the center of the pivotalconnection between the ram and the lever connected therewith, themovement of the pivotal connection being synchronized with the crankduring the draw ing stroke movement thereof to cause the resultantmovement of the ram to be at a substantially constant rate and less thanthe maximum speed of the crank pin so that the draw stroke of the ramoccurs during movement of the crank substantially in excess of 180, thepivotal joint being returned to the aforementioned line at substantiallythe end of the drawing portion ofthe revolution of the crank pin wherebythe maximum pressure exerted by the crank on the ram is through astraight line linkage. V

Another object of the invention is the provision of a new and improvedpress of the character referred to in which the pivotal joint of the twolevers forming a toggle linkage interconnecting the crank pin and ram ismoved in an elliptical path during each revolution of the crank, theelliptical path extending across the line through the axis of the crankshaft and the center'of the pivot between the ram and the leverconnected thereto, the pivotal connection having its greatest excursionfrom the aforementioned line during the. return stroke movement of thecrank pin whereby the crank pin and levers return the ram to itsuppermost position during movement of the crank shaft through an'angleappreciably less than 180.

The invention resides in certain constructions and combinations andarrangementsiof parts and further objects and advantages will beapparent to those skilled in the art to which it relates from thefollowing description of the preferred embodiment described withreference fit to.the accompanying drawings forming a part of this2,781,015 Patented Feb. 12, 19 517 ice Fig. 3 is a schematicrepresentation of the relative movements between certain parts of thepress mechanism throughout a cycle of operation;

Fig. 4 is a graph representing the speeds of the die slides or rams of aconventional crank operated draw press and the press shown in Figs. 1and 2; and

Fig. 5 is a graph illustrating the relative pressure-inches stroke of aconventional crank operated press and the press shown in Figs. 1 and 2.

Referring to the drawings, the crank operated draw press shown comprisesa conventional frame 10 having a die bed 11 and spaced upright guides 12in which-a die slide or ram 13, which may be of any suitableconstruction, slides vertically. The ram is adapted to carry asuitablepunching die which cooperates with a die attached to the bed to form arelatively deep draw in a metal blank. The dies are not shown as theyare well known to the trade, nor is the usual blankholding meanscomprising die cushions, pressure pads, etc. The particular press shownhas a drawing stroke of approximately fifteen and one half inches andthe dies will draw metal during approximately seven and one half inchesof the stroke, it being understood that a separation between the dies ofat least the depth of the draw is required to permit removal of thedrawn Work.

A crank shaft 16 is suitably journaled in the upper part of the frameand is driven by a pair of bull gears '17, 18 attached to the endsthereof. The bull gears are driven by pinions 19, only one of whichappears in the drawings, which are supported on a drive shaft 20 at therear of the press. The shaft 20 is preferably driven by an electricmotor 21 through a conventional one revolution clutch mechanism 22 whichmay be of any well known construction and includes a suitable controldevice such as a push button, pedal or lever, not shown, which isactuated by the press operator to cause the clutch to drive the shaft 20and rotate the bull gears 17, 18 through one revolution in acounterclockwise direction as viewed in Figs. 2, 3.. The details of thedriving mechanism for the shaft 16 are not shown since such drives arewell known in the'art. The crank shaft 16 has a crank pin or eccentric24, and in the particular press shown, the eccentric has a throw of fiveinches; that is to say, the center of the eccentric is otfset from theaxis of the crank shaft five inches. 7

The eccentric 24 is connected with the ram 13 through a bell crank leveror eccentric strap 25 journaled thereon and a link or lever 26 pivotallyconnected at one end to the arm 27 of the bell crank lever 25 and at theother end to the ram 13, the arm 27 and link 26.forming a toggle-likelinkage. The arm 27 of the bell crank lever comprises two spaced flanges28, 28 between which the upper end of the link 26 is received. This endof the link has a tubular bearing therein for receiving a wrist pin 31supported in openings through the'flanges 28, 28'. The lower end of thelink 26 is pivotally connected to the ram 13 by a knuckle joint 32. Thislinkage between the eccentric 24 and ram is similar to a toggle and byoscillating the bell crank lever '25 about the eccentric, the center ofthe joint comprising the wrist pin 31, which maybe termed the knee ofthe linkage, can be shifted from one side to theother of a line a, whichextend's" through the axis of the crank shaft and the center of'thejoint 32, to thereby raise the ram 13 or produce-relative line of thepress and, as vi'e wed'in Figs. 2, 3, the left hand side thereof isreferred to as'the forward or front side and the right hand side isreferred toasthe rear side. i V v l 7 'By shifting the joint comprisingthe pinfil forwardly of the line a and returning it to the line duringthe down- 7 ward sweep of the eccentric 24, the resultant rate ofmovement of the ram downwardly can be constant and substantially belowthe speed at which it would move joint comprising the pin 31 to the'rearrof the 'line -a during the .up-sweep of'the eccentric,the.1'esu1tant-,.upward movement of the ram 13 is substantially inexcessof the speed at which it would moveif connected to'the eccehtric'by asolidpitman, and the return stroke of the ram l3r can be .eflected byconsiderably less than 180 rotation of the eccentric. V

According to theinvention the bellicranklever 1s tric -so' that thejoint Iformed hythe pin :31 moves in if connected to the eccentric by .asolid;pitman,..as in,

- conventional crank .pressconstructions. By shifting the oscillated ihitimed relation to the rotation ofthe eccenan elliptical path dy as seenin 3, which intersects V the .verticalcenter line a, and its excursionto the forward side of the lineis appreciably .lessthan 11131168.!- tvardly ofj'theline. The center :of therj oint formed hy Ethe.pinf31coincides with lline a at the timetheeccentric 1Z4reaches the endo'f its downsweep at whichtime its lcenteris'likewise coincident withthe line a so that the ings in the ends thereof and the bearing in.oneend .is

pivoted to the bracket 37 by a wrist pin 38 which Vextends therethroughand is supported-in openings through two spaced parallel. lugs 39 of thebracket, and-the other end of theilihkfifi hasits'hean'ng pivoted to thearm of thclhell crank lever 25 by a wrist pin 42 extending therethroughand supported-inopenings .in two spaced. j lugs 45, 44 which'comprisethefarm 37 of the bellcrank levers-25; .Theicenter of the pivotpin- 42liesona lihe extending at .about 135 from a line through thecenters'of .theeccentr'ic '24 and the joint comprising the ,pm 31; aridwhenfthe shaft .16 rotates .the., ec'centric,' ihe link causes the.center of the pivot pin-42, to

' travel in an, are extending at apbfoximately from thefhoiizonteillinethrough theaxis vof theehaft'lfi.

The line. described which extendsnthrough 42 is,

if: =eifect, arm 35' and it will he vseen thatiitleittends into thequadrant ihounde'd bythe vertical -.center,line a and it'hehoriiont-alline .thr'ough the axisandinto which I the eccentricmoveswhenit;crosses,the'vertical-center line inxthe initial movement thereof toeffect a d ra wstroke. By anchoring the arm 35 0f the bell crank lever25,as described, the'hell cranklever 25 is.oscillated about'theeccentricidastthe latter is rotatedtto effect the shifting 1 "off thejointaat the pm and actuate ,the .ram asujescribed. j

' uis mentiohed previously the ,press shown by .way' of examplefhasa'ram stroke-.01"; fifteen and onerhalf inches; and j't o oota inithemost desirable operating characteristics of V the ,pressithei effective;lengthof thc earm 21 me i sd m- Cente Of secse n'r wane-ax f: th P 31 i"se le 'm a h s; h u ts h ,q lete ez i m asured 'fr'ornlthe, .cent er ofpinfil tolthe center pf w[the .32 Tris; twenty-.three incheg" theilength of the i l 'i t xmsest ts r m h heat 10f he ecceni i241 ofpin 38.is located from the vertical center gline quarter inches belowthehorizontal lineithroi gh' the axis pin locations and lengths ofrthearms, lever and link "should remain in proportion to the strokeapproximately as indicated.

It is to be understood that only those parts of the press have beenshown and described which are essential to the understanding of themechanism for operating the ram, and that additional well knownstructures, such as an adjusting mechanism-between the ram and the link26, have not been shownas they are well-known in the trade. 1

. The operation of theram canjbe readily uhders'tood by referring toFig. 3 which shows various elements of the press schematically and intheirrespective positions at different angular positions of thecrankshaft. When the press is idle, thecrankshaft 16 is in a position inwhich the center of the eccentric 24 is at 24a and'since link 36'limitsor guides the portion of the arm 35 in which the wrist pin142 issupported in the arcuate ,path b the, pin .42 is at 42*1andthe ebell-cranklever 25 is thus positioned'about the eccentric so that the jointcomprising .wrist ,pin .31 .is at 31 which is (considerably to the rearof .the vertical .center line, and the end of link 26 comprising thejoint 32 between the link and ram '13 is at 32 the upperendofIits travelor stroke.

As counterclockwise rotation .of thecrank shaft .is initiated, .theeccentric is movedinithe circular .path 0 up- Wardand across center linea, moving the. joint :com-,

prising wrist pin .42 upwardly :along arc .b which ,tilts the bell crank.lever25 clockwiseabout the eccentric and moves the joint comprising pin31 along the e1- liptical path d toward ,the center linea therehytendingto .straightenlthe angle-.between arml7 .of the bell crank lever 25 andthezlever 26 whichvlowers the i-ramihrough a .greater distance than .theverticalv movement of the j ;eccentric.

7 As the eccentric .sweeps through the .first guadrant at the left ofvertical .line 1i, the crank --leve r' :25 con 7'tinuesclockwiseabout,theteccentric andwhen the cenportionoflitss'troke.As the eccentric ,moves "to point 24. 'thejoint. atpin .42fis.movedtoA-Z and the.bel1- f3 ,1at thejleftorfront ofl thelinemandathereby break the straight anglebetween the arm 2 :7,and lever26 which actionitends to. raise lthe ramj j The eccentric at this point,7 however, is .sweepingdownwardlyat a rategin aexcess of the rate atwhich the breaking of the ar-113 21 lve'rlfiitend tmraise theiram s13solthat the resultant rate of descent of the ram is thealgebraicumgof'these e twofactors and-the joint $2,;is,at132, is nj'the'drawmortion to'fdtssttoke. When athelcentcr :of ithe eccentric reaches25 it :is traveling .at ritsl greatest rate a ter of theeccentric-reaches the pointv24b .the respective joints comprising pins42 .and 31 are at ,42 andSlP,

and theangle' between arm ;27 and-lever 26 israpidly approaching l..

Thecenter .of the joint 32 is then .at 32 and'theiamis approachingthelow'enhalf or draw lever is: swung to move the joint -,c'on 1prising;pin 31 ;to

in the vertical componentand: at zthe tsame time 1 thezjo'intcomprisinglpinl is approachingiitsvmaximum 'excursion 4' of the crank.shaft. It is to he understood that these 4 mi gn wo anlyxample d ermeyhen immers s hayin fis smaml strok ;al oug .th

-,.ofthe eccentric." i U g rth'elcen terof tlIe'eccentric reapproachesgline' a,

bellerank3-lever25 istm'oved counterclockwise thereabout toswingithi'ezjoirit'icoinprising 'pin' 31 back toward ine V p g V V 7 Va; thecebylradding Io ithedowhwardtmovement of he gguide link32measureg1 trornithe .center ofg pin A w 7 35 to the center of pin3124s sixteen inches; The axis I to the frontzof line-a and increasingthe break ifrom the .straight r angle-between ,arm..27 :and1 lever' 26'so' that {the rate at .which it tends 'to'lrais'e the -ram isincifeased 'toi closely :corre spohd itotthe increase jryth'edownwardfrate' the resultant straight line linkage. g V I v As the crankshaft continues its rotation and moves the eccentric in its upwardsweep, the link 36 forms a pivot about which lever 25 rotates wherebythe joint comprising pin 31 is swung .wide and rapidly to the rear ofthe line a and imparts a quick withdrawing movement to the ram 13. Thiswithdrawing action of the levers 25 and 26 combining with that of theeccentric quickly returns the ram to its uppermost position, at whichpoint the crank shaft is stopped.

In connection with thetransmission of force from the eccentric to theram, the excursion of the pivot joint at pin 31 forwardly of thevertical center line a during the draw stroke is limited so that'thelever 26 is not shifted over about 11 from vertical whereby the lateralthrust on the ram guides is low and will not be sufficient to causeappreciable wear or inaccuracy in the operation of the dies. It will benoted that the maximum pressure is applied at or near the in-lineposition of the arm 27 and link 26.

It is apparent that the downward or drawing stroke of the ram iseffected by an appreciably greater angular movement of the crankshaft 16than that required to return the ram to its uppermost position. In thepress shown, the drawing or working stroke occurs during about 220movement of the crankshaft as against 180 movement of the crankshaft ofa conventional crank operated press. Thus, the R. P. M. of thecrankshaft of the improved press can be substantially increased overthat of a conventional crank operated press without increasing themaximum drawing speed of the ram.

The relativerates of travel-of the ram of the improved press and that ofa conventional crank operated press having the same length of stroke isillustrated in the graph shown in Fig. 4. In this graph line 50represents the lineal movement of the ram 13 relative to the angularmovement of the crankshaft16 which is represented by the parallellongitudinally extending lines which are spaced from one another torepresent ten degrees of crankshaft rotation. The zero. degree orstarting position of the crankshaft is represented by the first line atthe left end of the graph. It will be seen that during the first onehundred degrees of rotation of the crankshaft the ram is lowered throughapproximately the first half of the. draw stroke, which merely bringsthe dies together. The last half of the stroke in which the work isdrawn by the dies, the rate of travel of the ram or the movement thereofper degree of rotation of thecrankshaft'is substantially constant, untiljust before the end of the stroke. The last half of the stroke that is,the working or drawing portion of the stroke is effected by about onehundred and twenty degrees of rotation of the crankshaft. The returnstroke of the ram occurs in about one hundred and forty degrees ofmovement of the crankshaft. Broken line 51 of the graph illustrates themovement of the ram of the conventional crank press and it will be seenthat the movement of the ram per degree of rotation of the crankshaftduring the greater part of the drawing portion of the stroke isconsiderably in excess of that of the improved press. As a result, theR. P. M. of the crankshaft of the conventional press must beconsiderably less so that the maximum permissible draw speed is notexcessive. In fact, the R. P. M. of the improved press can be 82% higherthan that of conventional crank presses having like ram strokes.

' The improved press not only is capable of operating at a much higherspeed than conventional crank operated presses of comparable strokes,but it is capable of delivering considerably greater tonnage to the ramfrom equal power input. Referring to Fig. 5, the graph thereinillustrates tonnages by the vertical appearing lines and the depth ofthe drawing die is indicated by the horizontal appearing lines spacedapart to represent half inches of depth of the die, the bottom of thedie being represented by the bottom line. The broken curved line 54represents the pressure curve on the ram of a conventional crankoperated press and the curved line 55 represents the pressure curve onthe ram of the improved press having the same power and ram stroke asthe conventional press. It will be seen that the improved press deliversconsideraly greater tonnage to the ram in the upper part of the drawingstroke and that the tonnage delivered to the ram of the conventionalpress does not approach that of the improved press until the last inchor so of the stroke.

It is apparent that the objects enumerated as well as others have beenattained and that a new and improved press of the. character referred tohas been provided which materially increases the speed of operation ofmetal drawing operations over conventional crank operated presseswithout exceeding safe drawing speeds, and that the efliciency of thepress with respect to the tonnages deliverable to the punch ram issubstantially increased over that of conventional crank operatedpresses. While but one form of the invention has been shown anddescribed, it is our intention to cover'hereby all other forms,modifications and adaptations, thereof falling within the claimsappended hereto.

Having thus described our invention, we claim:

1. In a draw press, a frame, an eccentric journaled in said frame, meansto rotate said eccentric in one direction about a fixed axis, a ram,means to move said ram in a drawing stroke comprising two leversconnected together by a pivot joint, one of said levers being journaledon said eccentric and the other lever pivotally connected with said ram,and means operatedin synchronism with the rotation of said eccentric tomove said joint to one side of a line through said axis and the centerof the pivot connection between said ramv and said lever. connectedthereto during the ram drawing stroke movement of said ram and to returnsaid joint substantially to said line as said eccentric'reaches theextremity of its drawing stroke movement whereby the centers of saidjoint and said eccentric lie substantially on said line, and 0perable tomove said joint to the opposite side of said line during the ram returnmovement of said eccentric, the excursion of said joint on' saidopposite side of said line being substantially in excess of itsexcursion to the first mentioned side of said line.

2. In a draw press, a frame, a ram slidable in said frame in a drawingstroke, an eccentric journaled in said frame, means to rotate saideccentric in one direction about a fixed axis, a drive between saideccentric and ram comprising two levers connected to one another by apivot joint, oneof said levers being pivotally connected with saideccentric and the other of said levers pivotally connected with saidram, an arm rigidly connected with the first mentioned lever andprojecting into a quadrant defined by a line in a plane containing saidlevers extending through said axis and the center of thepivotalconnection of said ram and said lever connected therewith and a secondline through said axis and normal to the first mentioned line and saidaxis and which quadrant is initially entered by said eccentric passingthrough the first mentioned line in moving said ram in its drawingstroke, and a pivoted lever for guiding a point on said arm in anarcuate path extending at approximately 45 with respect to said secondline and having its pivot point to one side of said second line and inthe quadrant adjoining the first mentioned quadrant and on the otherside of the second line whereby said one lever is oscillated by rotationof said eccentric about said axis to swing said joint in an ellipticalpath intersecting the first mentioned line.

3. In a draw press, a frame, a ram slidable in'said frame in a drawingstroke, an eccentric journaled in said frame, means to rotate saideccentric in one direction about a fixed axis, a drive between saideccentric and ram comprising two levers connected to one another by apivot joint, one of said levers being pivotally connected with saideccentric and the other of said levers pivotally conjframe at a point ina-p laner parallel to said second line' between said axis andram and ina quadrant adjoining {the first mentionedquadrant, said link projecting'into' said quadrant and being pivotally connected to said arm.

'4. V In a draw press, a frame, a ram vertically slidable in said frame,a first le ver pivotally connected at one 'end to said ramjfcrreciprocating 'the latter, the pivotal connection between saidlever'an'd sai'd ram'moving along a vertical line, "an'eccentricrotatalily supported in said frame with its axis ofrotation-normal to and intersecting said line, aneccentri'c strap.rotatably supported by'said eccentric and including aniarm pivotallyconnectedto the other end of said lever'and "forming a "toggle "linkagetherewith, lever means connected to said strap for positioning said amalong said line whenthe center ofsaid eccentric is at'its lowest pointin its'path o'f rotationand for causing the pivotal connection togswingto one side of said line for more than 180" but less than 270 'ofrotation of the eccentric from its lower position and then' "to swing.to the other side ofsaid line until the center of said eccentric againreaches its lowestpoint with'the' movement ,Gf the pivotal connectionbetween said arm and said'lever 'defining a substantially ellipticalpath 'gen erally transverse jtogan'd intersecting said line with theexcursionoffthefcoiinection to the first-mentioned side of the :linebeing substantially greater than its excursion "to the second-mentionedside of said line. 7 I "5. :Ina drawrpress, a frame, aram verticallyslidable in said frame, a first lever ,pivotally connected atone end tosaid rarn for vertically reciprocating theleitter, the pivotalconnection between said lever and. said ram rmovin said frame withitsaxis of rotation normal'to and intersecting said line, an eccentricstrap rotatably sup- 7 ported by said eccentric and including afirstarmpivota'bly :butl ess than .270? tofiotationof the centerof theeccentric from its lowest position and then to swing :to the other" sideot fsaid :line until the center of said eccentric again reaches'itslowestipoint with the movement of'the :pivotal connect-ion between saidarm and saidlever defining a substantially elliptical path ge'nerallytransverse to and intersecting said line and with the excursion of saidpivotal-connection-to the-'first-menti'oned 'side of the line beingsubstantially greater than its' excursionto'theisecondmentioned siderof'said line, I

6. In a draw press, a frame,;ia iall lf -Ve'lfic ally 'slida'ble in saidframe, a first lever pivotally connected at one 7 end to said ram forreciprocating' the latter, the pivotal connection between said lever andsaid ra'rn moving along a vertical line', an eccentric rotatablysupported in said frame with'its :axis of rotation normal to andintersecting said Hire, an eccentric strap rotatably supported by saideccentric and includinga first arm pivotably connected to the other endof said lever, forming a toggle linkage therewithand 'a second'arm-defini'ng an obtuse angle with 5 saidsfirst arm and extending intothe quadrant in which thex'cen'ter :of said 'eccentric begins itsdownward movement upon rota'tion thereof, a pivoted 'lever pivotallyconnected to said second arm for constraining a point thereontoxmove-al'ong-an arc in said quadrant and for positioning sa'id firstarm along said'line When-the center of said eccentric is-at its lowestpoint in its path of rota- 'tion and to cause the pivotal connection toswing to one side of said linefoi' more than 180*but less than 270 ofrotation of the'eccentric from its 'l'ower'position and athen toswing'toitheother sideof said line nntilthe center of said eccentric againreaches its lowest point with "the movement {of *the pivotal connectionbetween said arm and said lever defining a substantially-elliptical pathgenrera lly transverse to and intersecting-Said line with fill!)excursionof the connection to "the first-mentioned side a ing along avertical line, an eccentric rotatablysupportedi connected to the otherend of said lever forming a toggle r 7 linkage therewith and a secondarm defining an obtuse angle with said first arm and extendingint'o thequadrant 7 in whichfthe center ofsaid eccentric begins itsdown'wai'dmovement uponrotatiori thereof, lever means connected to said second arm'for'positioning said first arm along saidiine when the center of saideccentric is at its lowest 7 7 point in its path of rotation andfiorconstraining the pivotal connection between said first farm andf-saiddever to swing to one side o ffsa'id line forjrnore than jl" ofthe line being substantially greater than its excursion V to thesecondmentioned'sideof said =line, -'and means pivotany supporting thelast sai'd lever in the quadrant entered by the center of the eccentricupon leaving the jfir'st sa'id quadrant. I

'References Citedm the meet this patent" 2,688,296 7' "panly u g nSepte7, 1954

